Search results

  1. W

    Axial Thrust

    If I am designing my axle for a worse case scenario, I need to take this possible axial load into account? My initial thought that was when the user is going around a corner, a lot of the users weights and the weight of the wheelchair frame will be transfers down the axle and this would be my...
  2. W

    Axial Thrust

    I'm in the process of calculating my combined stress on an axle I am designing, I have calculated the bending and torsional stress, however I need to calculate the direct stress in the axle. In order to do this I need to know the axial thrust in my axle, I understand what axial force is but I am...
  3. W

    Steel tables for calculating axle diameter

    After looking over my calculations, I've realised I had my bending moment slightly too high, therefore my bending stress is wrong. My bending stress is actually 63MPa.
  4. W

    Calculating gear ratios for a drivetrain

    I took the rolling resistance from the below table taken from this link http://www.engineeringtoolbox.com/rolling-friction-resistance-d_1303.html Perhaps a higher one is more suited for rough terrain? Therefore, 75/3000=0.25 I want my answer to be 1.4 (walking speed), so I need to decrease...
  5. W

    Steel tables for calculating axle diameter

    No there isn't, my design has one axle per wheel, so the other wheel is supported by a mirror image of this axle.
  6. W

    Steel tables for calculating axle diameter

    Ah yes, I forgot to convert to MPa. I am familiar with deflection however not sure how to calculate it under these parameters, could you give me some pointers?
  7. W

    Steel tables for calculating axle diameter

    0.063kNm * 0.01m / 7.85398 x10-9m4 0.00063kNm2 / 7.85398 x10-9m4 80214kNm-2 (Not too sure on these units, what should they be?)
  8. W

    Steel tables for calculating axle diameter

    Thanks, I will do. Now that I have this bending stress for a 20mm diameter shaft, how do I decide if this is suitable for my application? Or do we now look at torsional stress?
  9. W

    Steel tables for calculating axle diameter

    Thank you. Second moment of area being calculated by pi/4 * r^4 ? By doing this I get 0.063 * 0.01 / 7.85398 x10-9 = 80214 as the bending stress?
  10. W

    Calculating gear ratios for a drivetrain

    What kind of information would be required to take rough terrain in account? Can you clarify why this would be at 0.25 m/s? I thought I was calculating the output power, and my initial calculation had found the output to be too high at 300N?
  11. W

    Steel tables for calculating axle diameter

    By maximum stress level is that the bending stress? which is My/I m= moment y= radius I = moment of intertia
  12. W

    Steel tables for calculating axle diameter

    1. Only the load shown in the previous diagram and this axle will be manually driven at low speeds. 2. Between 10mm and 23mm. 3. Preferably a stock bar sized would be used for the axle to keep costs down, so the closest one to the needed axle. 4. I am yet to select my bearings but only plan...
  13. W

    Calculating gear ratios for a drivetrain

    I've had a re-read through of the thread and answered most of my questions, thank you. I initially did the calculations using a gear ratio of 0.2m diameter for the driven and 0.1m diameter for the driver. I worked it out as getting an output of Fv=301.7N with the method you have shown. Looking...
  14. W

    Steel tables for calculating axle diameter

    Thanks for your help, I'll look into this ASAP. Regarding axial thrust, is there a way to determine what this load is for my circumstance? I understand it may not be a formula, just what factors I need to consider.
  15. W

    Calculating gear ratios for a drivetrain

    Thanks a lot for your help, I have a few questions regarding this method. 1. Am I correct in thinking I determine my own gear ratios to begin with and carry out the equations, deciding if my end result is correct and changing the ratio accordingly if required? 2. For calculating hand velocity...
  16. W

    Calculating gear ratios for a drivetrain

    This is what the initial post was about, although now I'm unsure exactly where I've been helped with this due to the multiple different ideas from different users (I understand that's the point of a forum). Are you able to clarify how I go about calculating this? Not taking into account any...
  17. W

    Calculating gear ratios for a drivetrain

    Is there even a point in me having two gears then? Besides from locating the lever arm away from wheel axle? It seems that I am not getting any mechanical advantage at all from having two gears.
  18. W

    Steel tables for calculating axle diameter

    Are the equations shown here https://theconstructor.org/structural-engg/solid-mechanics/combined-bending-direct-and-torsional-stresses/3704/ what I need to use to do this? I've calculated my bending stress as 50.4 and my torsional stress as 10.2 using the method shown in that linked page. I'm...
  19. W

    Calculating gear ratios for a drivetrain

    I am just trying to work out what the size of each gear should be for a use over mainly rough terrain. Is this possible? Or will the gears just be the same size with the power provided to the wheels being varied by where the user pushes the lever?
  20. W

    Choosing a bearing tolerance

    Not sure how this helps me regarding tolerances?
  21. W

    Steel tables for calculating axle diameter

    By 'carrying torque' to mean will it be being driven by something? If so, then yes
  22. W

    Steel tables for calculating axle diameter

    Now that I have my bending moment, what is the next step towards calculating my shaft diameter?
  23. W

    Choosing a bearing tolerance

    This sounds suitable for my design. What about considering tolerances?
  24. W

    Choosing a bearing tolerance

    I'm currently in the process of designing a bearing housing for an axle. Unfortunately I am not 100% on the diameter of my axle yet but I want to have a clear understanding what tolerances to use on my axle to bearing bore and bearing outer diameter to the bearing housing. I've looked over the...
  25. W

    Steel tables for calculating axle diameter

    0.08m to first bearing, 0.2m to second bearing from first bearing
  26. W

    Steel tables for calculating axle diameter

    Hopefully the above diagram helps. I have calculated my reactions as 1.099kN on the left bearing and -0.0314kN on the right bearing. Giving me a bending moment of 0.063. This over the tensile strength of steel (274 mPa) is 0.00023. So I believe this to be my plastic modulas? (Sx) and I am...
  27. W

    Simple bending moment calculation

    Thanks a lot for your help.
  28. W

    Simple bending moment calculation

    Hi, Really need some help with figuring out the max bending moment in the diagram shown below (I'm aware this is extremely simple but time and stress appear to have the better of me, so any help is appreciated) I think I've worked out the reactions at each support by doing m=wL as the...
  29. W

    Calculating gear ratios for a drivetrain

    The front two wheels are bicycle wheels of about 660mm diameter and then a rear castor wheel which is about half the size which allows the wheelchair to steer.
  30. W

    Calculating gear ratios for a drivetrain

    Are you referring to the size of the gears or the actual wheels?
Top